AC and SC, Scapula & Shoulder Girdle review Flashcards
Describe the acromioclavicular joint
- where acromion process of scapula is meeting up with lateral end of clavicle (ALWAYS indicate which side! Diff movements and form 2 diff joints)
- common place for injuries (separated shoulder)
Describe the joint and articular surfaces of the AC joint
- joint surfaces of acromion process lateral end of scapula are small, very shallow
- flat & shallow = not a lot of ROM because big idea is to hold scapula that clavicle
- on the inside we find a articular disk just like SC joint: fibrocartilaginous disk sandwiched between the 2 ends of the bones
What ligaments hold the AC joint together?
AC (acromioclavicular) ligament, CC ligaments (coracoclavicular)
Describe the AC ligament
- reinforces The joint capsule and is thickest on the superior side of the joint
- not strongest stabilizer of joint
Describe the coracoclavicular ligaments
- attaches down to coracoid process
- a pair of ligaments
CONOID: medial side, coming up from the coracoid process to the conoid tubercle, to inferior aspect of clavicle
TRAPEZOID: off coracoid process, runs along trapezoid line on the inferior aspect of the clavicle. Helps prevent superior translation of the lateral end of the clavicle, keeping the AC joint together - The two ligaments help hold scapula up relative to lateral end of clavicle
Describe the coraco-acromial ligament
- doesn’t actually support a joint directly, just nearby AC joint
What effect does gravity have on AC joint ligaments?
- gravity wants humerus to go down
- scapula will also go down & coracoid process away from clavicle, stretches these ligaments
Describe the location and function of SC (sternoclavicular) joint
- medial end of the clavicle fits into concave spot on manubrium of sternum
- has a very important job! Gets lots of motion here that pivot off SC joint
ELEVATION
DEPRESSION
PROTRACTION
RETRACTION
What does the magnitude of actions @ SC joint mean for it’s ligaments?
We need lots of ligamentous support to keep joint stable
Name the ligaments and structure (s) that keep the SC joint together
- anterior SC ligament
- posterior SC ligament
- costo-clavicular ligament
- articular disk
Describe the SC articular disk
- similar to meniscus in knee, sandwiched between 2 bones and made up of fibrocartilage
- deals with compressive forces through the joint & shearing or frictional forces that occur there as well
- inside of joint capsule (that every synovial joint will have)
The SC joint capsule is reinforced by _
2 SC ligaments
Describe the anterior SC ligament
- comes from anterior side of the manubrium of the sternum
- comes up and lands on medial end of clavicle
Describe the posterior SC ligament
- does the same thing as anterior SC and has same attachments, just more posterior
Describe the costo-clavicular ligament
- named for it’s attachments
- comes in off superior aspect of costal cartilage on 1st rib
- travels superiorly to attach a long inferior side of the medial end of the clavicle
What happens to SC ligaments with retraction?
Stretches apart anterior SC ligaments
What happens to SC ligaments with protraction?
Opens up posterior side and stretches posterior SC ligament
Why can the clavicle resemble a teeter totter?
- axis of rotation set by costo-clavicular ligament instead of in middle: holds clavicle down and creates axis of rotation
- gravity wants to pull the arm down (which is attached to scapula so that goes down also, lateral end of clavicle & scapula go down)
** when lateral end goes down, medial goes up (SC ligaments need to hold the medial end down to prevent this)
Name the major joints of the shoulder girdle
AC joint
SC Joint
Describe the shoulder girdle
- clavicle, scapula and muscles (NPT HUMERUS)
- clavicle anchors us medially to the sternum, wraps around laterally and joints up with the scapula
- 1 big long continuous strip of bone with V shape (sternum>clavicle>scapula)
Describe the bony structures of the shoulder girdle
- 2 angles (superior and inferior)
- 2 borders (lateral and medial/vertebral)
- glenoid fossa
- Spine of scapula+2 fossae (infraspinous and supraspinous)
- 2 processes (acromion and coracoid)
**Draw this out!!!
What actions happen at the shoulder girdle?
ELEVATION-DEPRESSION
PROTRACTION-RETRACTION
SUPERIOR/INFERIOR ROTATION OF SCAPULA
WINGING
Describe elevation
- Superior rotation of scapula, follows contours of rib cage (curve)
- pivoting off SC joints, and lateral end of shoulder girdle lifts up while pivoting around medial end
Describe depression
- inferior rotation of scapula
- in general shoulder girdle moves to position humerus somewhere in space (“driver” for the humerus)
Describe protraction
- bringing scapulas forward & sliding apart from one another
- lateral end of shoulder girdle moving forward
- closing up front of chest, opening back
Define retraction
- lateral ends of shoulder girdle drop back
- scapulas come closer together
Scapula rotates on the _
Thorax
Define superior rotation of scapula
- glenoid fossa goes up
- humerus goes up
- inferior angle goes farther away from midline of back
Define inferior rotation of scapula
- glenoid fossa goes down
- humerus goes up
- inferior angle moves closer to midline of back
Define winging of the scapula
- scapula is not anchored to rib cage (no ligament, otherwise it would’nt have ROM): held exclusively by muscular control
- isn’t always at work & scapula can lift away from ribcage
- looks like you develop “wings”, especially with anterior tilt
- not great cause this could mean less stability in other parts of the arm
Describe the coracoid process
- sticks our like finger into anterior aspect of the shoulder above & medial to glenoid fossa
- points forward and laterally
- sticks out for a reason! Important for us when muscles attach
Describe the acromion process
- extension of the scapular spine
- enlarges & forms process
- can feel it on yourself!
- coracoid process on front side
Describe the superior angle of scapula
- point on the medial superior side of the scapula
- muscle will attach here
What is the function of the glenoid fossa?
- shallow socket for humerus
Describe the SOS (spine of scapula)
- ridge of bone running along posterior side, long & narrow
- has shallow fossa above & below
Describe the medial/vertebral border of scapula
- closest to vertebrae
- lots of muscular attachments
Describe the inferior angle
Point on the inferior side of scapula
- more muscular attachments here
